Automatic vehicle operation systems which control the propulsion and braking equipment on board a vehicle to bring the actual vehicle velocity into agreement with a command velocity have been available in the art for many years. Systems of this type are particularly useful in mass transit applications which involve high speed and close headway operations of vehicles. Automatic vehicle operations in these applications eliminates the necessity for vehicle operators with the associated risk of operator error. Although failsafe systems, which limit the consequences of operator error, have been in use for an even longer period of time, these circuits do not prevent operator errors from reducing the vehicle speed to a speed below an optimum or allowable speed. Therefore, one object of the present invention is to provide an automatic vehicle operator system which eliminates the necessity for a vehicle operator.
Mass transit applications of vehicle control systems ordinarily encounter high speed and close headway vehicle operation requirements. A characterizing feature of most mass transit vehicles is their relatively light weight in comparison to long-haul vehicle operations. The associated high acceleration and speed requirement can result in large acceleration and deacceleration forces exerted upon the passengers of the vehicles. At the very least three large acceleration and deacceleration forces can cause discomfort and in some instances can even be dangerous. It is therefore another object of the present invention to provide an automatic vehicle operation system which limits the acceleration and deacceleration forces to a predetermined maximum. Since these forces can be caused by grade conditions in addition to rate of change of velocity, the acceleration control circuit takes into account not only the rate of change of velocity but also the grade over which the vehicle is traveling in order to limit the total acceleration forces to a predetermined maximum.
Jerk, which is the rate of change of acceleration, can also cause passenger discomfort and/or possibly passenger injury. Therefore, in addition to controlling the maximum acceleration forces, the maximum jerk is also controlled to be within predetermined limits. The jerk is not directly controlled. The circuit controls the maximum rate of change of tractive effort. In order to keep the jerk within predetermined limits the maximum rate of change of tractive effort is limited in light of the vehicle loading. As a result, the jerk is controlled within a predetermined maximum regardless of vehicle loading.
The vehicle is also responsive to one of two different stop commands. The difference between the two stop commands is that one stops the vehicle in a shorter distance than the other stopping command. In response to one of the two stop commands the vehicle registers the associated distance from the vehicle to the stopping point. As the vehicle proceeds toward the stopping point this distance is continuously decremented. The stopping profile generator continuously generates a signal proportional to this distance which is utilized as the command velocity for the vehicle. Thus, within the allowable acceleration and jerk limits, the vehicle comes to a smooth and precisely controlled stop.